Chuck for tools, especially screwdriver bits

ABSTRACT

A chuck ( 1 ) for tools, especially screwdriver bits with a polygonal section ( 2 ), has a polygonal cavity (3) for the insertion of the polygonal section ( 2 ). A wall ( 4 ) of the polygonal cavity ( 3 ) has a window ( 5 ) in which is disposed a pressure-piece ( 6 ) which can be displaced in the insertion direction (E) and which, in order to secure the inserted polygonal section ( 2 ) against being drawn out, is forced against the polygonal section ( 2 ), in a direction transverse to the insertion direction (E), by a sloping inner wall ( 9 ) of an actuating element. The actuating element is outside the window and is retained in a clamping position by a restoring spring ( 10 ), and, in a release position of the actuating element ( 7 ), moves aside out of the polygonal cavity ( 3 ) in order for the polygonal section ( 2 ) to be drawn out. The pressure-piece ( 6 ) is subjected to the action of a compression spring ( 8 ) acting counter to the insertion direction (E) and, upon displacement counter to the direction of spring action, moves aside out of the polygonal cavity ( 3 ).

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a chuck for tools, especially screwdriver bitswith a polygonal section, having a polygonal cavity for the insertion ofthe polygonal section, the wall of the polygonal cavity having a windowin which is disposed a pressure-piece which can be displaced in theinsertion direction and which, in order to secure the inserted polygonalsection against being drawn out, is forced against the polygonalsection, in a direction transverse to the insertion direction, by anactuating element outside the window, in a clamping position of thiselement, and which, in a release position of the actuating element, canmove aside out of the polygonal cavity in order for the polygonalclamping section to be drawn out.

Such a chuck is already known from DE 29 34 428 C2. In this document,the pressure-piece is configured as a ball and is positioned in awindow, which is associated with one of the surfaces of the polygon,such that it can be moved in the insertion direction. The window here isin the form of a slot extending in the insertion direction in the cavitywall. Outside the window, the slot is closed by an actuating elementwhich acts on the ball by means of a sloping flank. The actuatingelement, which is in the form of a sliding sleeve, is biased by springaction in the actuating direction, which extends in the insertiondirection. If the polygonal section of a bit is inserted into thischuck, then an annular slope which is arranged at the rear end side ofthe bit displaces the ball in the insertion direction within the window,in which case the ball, running along the slope of the actuating sleeve,moves out of the polygonal cavity in order to increase the size of thefree cross-section. The ball, finally, runs over the end edge of the bitand rests on the surface of the polygon of the polygonal section. If thebit is subjected to a pulling action counter to the insertion direction,then the ball rolls, on the one hand, on the slope of the actuatingsleeve and, on the other hand, on the flank of the polygonal section.Since the two surfaces are located in a wedge relationship to oneanother, this results in clamping.

The disadvantage is that this clamping mechanism does not function whenthe bit is oriented upward and the ball, in the rear section of thewindow, lies freely between the flank of the polygonal section and theslope of the actuating sleeve.

The prior art also discloses latching-ball mechanisms in the case ofwhich the ball is located in a window-like cutout which is made in theactuating sleeve and the extent of which in the insertion directioncorresponds substantially to the ball diameter, so that the ball can bedisplaced substantially only transversely to the insertion direction ofthe bit. The ball is then forced into its blocking position exclusivelyby the sloping flank of the actuating sleeve. In the case of this chuck,the ball enters into a corner cutout of a bit. Accordingly, it isassociated with the edge of the polygon rather than with the surface ofthe polygon. In the case of this chuck, the actuating sleeve has to bedisplaced into the release position in order for the bit to be inserted.

SUMMARY OF THE INVENTION

It is an object of the invention to develop the chuck of the generictype in a functionally advantageous manner.

The object is achieved by the invention based on the pressure-piecebeing subjected to the action of a compression spring acting counter tothe insertion direction and, upon displacement counter to the directionof the spring action, can move aside out of the polygonal cavity. Thesubject matters stated in the rest relate both to advantageousdevelopments of the subject matter and, at the same time, to separatetechnical solution proposals which are independent thereof and of theobject mentioned above. It is proposed here, in particular, that thepressure-piece is a round piece. It may be a ball in particular. It ispossible for the pressure-piece, as is known in principle from the priorart, to be formed by a sloping inner wall of an actuating sleeve whichforms the actuating element. The window is preferably associated withone of the edges of the polygon of the sleeve, so that thepressure-piece can also enter into a corner cutout of the polygonalsection of a bit. It is also the case, however, that bits which do nothave a corner cutout are retained merely with edge abutments by thepressure-piece. By virtue of an appropriate selection of the diameter ofthe round piece, the latter can rest merely on those points of thecorner cutout which are formed by the peripheral edges of the cornercutouts which meet at a point. Genuine punctiform support is thenprovided. These geometrical conditions are present, in particular, whenthe radius of the round piece corresponds to the width of the cornercutout. It is also possible for the actuating element to be displacedfrom the clamping position into the release position against the forceof a restoring spring. It is advantageous here if the direction ofaction of the restoring spring corresponds to the direction of action ofthe compression spring acting on the pressure-piece. The two springsthen act counter to the insertion direction. The pressure-piece may beretained in the window by means of a carrying-shoulder support, as isknown in principle in the prior art. In this case, it can penetrate intothe cavity to such a depth that it projects into the abovementionedcorner cutout of the polygonal section. In a particularly preferredconfiguration, the window is located level with this corner cutout, sothat the rear end surface of the bit or of the polygonal section engagesagainst the base of the polygonal cavity. If a commercially availablebit is pushed into the polygonal cavity of the chuck, then the annularbeveling, formed by a chamfer, at the end of the bit displaces the ball,which forms the pressure-piece, in the insertion direction, and the ballas a result compresses the compression spring and rolls or slides alongthe sloping inner surface of the actuating sleeve. In this case, theball is displaced not only in the axial direction of the cavity, butalso transversely thereto, namely out of the cavity. The freecross-section for the insertion of the bit thus increases in size. As isalso the case with the generically determinative state of the art, thebit, finally, can be pushed through beneath the ball until, for example,the rear end surface of the bit acts on the base of the cavity. Thespace between the edge of the polygon of the bit and the sloping innerwall of the actuating sleeve forms a wedge-shaped space which taperscounter to the insertion direction the compression spring presses theball. The ball is thus retained in a clamping position by thecompression spring. If then, irrespective of whether the ball ispositioned in a corner cutout or merely rests on an edge of the polygon,the bit is subjected to tensile forces, this results in the ball tendingto be displaced in the direction of the gap, so that the clamping forceis increased. In order to free the pressure-piece, the actuating sleeveis moved into the release position. This results in the wedge-shaped gapbeing widened. The ball can then move aside transversely to theinsertion direction. If the ball is located, for example, in a cornercutout, it can pass out of the latter. If it is merely supported withclamping action on an edge of the polygon, then the clamping action iseliminated by the actuating-sleeve displacement.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is explained hereinbelow withreference to attached drawings, in which:

FIG. 1 shows a side view of a chuck, partly broken-away in the region ofthe polygonal cavity,

FIG. 2 shows a section along the line II—II,

FIG. 3 shows the detail designated III—III in FIG. 1, on a greatlyenlarged scale, with the actuating element located in the clampingposition but without any bit inserted,

FIG. 4 shows the illustration according to FIG. 3, but with theactuating element displaced into the release position and a bitinserted,

FIG. 5 shows an illustration according to FIG. 3 with the actuatingelement displaced into the clamping position and a bit inserted,

FIG. 6 shows an illustration according to FIG. 5, the pressure-pieceentering, in certain regions, into a corner cutout of the bit, and

FIG. 7 shows an illustration according to FIG. 3 with a bit beinginserted and the pressure-piece moving aside over the rear,chamfer-forming end edge of the bit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The chuck 1 has a polygonal insertion section (not illustrated) in orderfor it to be inserted into the chuck of an electric screwdriver or ofsome other power tool. Opposite to this clamping section, the chuck hasa polygonal cavity 3. It is possible to insert, in the insertiondirection E, into the polygonal cavity 3, which has a hexagonalcross-section, a polygonal section 2 of a bit which has this samecross-section. The depth of the polygonal cavity 3 may then be selectedsuch that the bit 2 engages with the rear end surface of the polygonalsection against the cavity base. The polygonal cavity 3 has a window 5in the region of one or more of the corners of the polygon (see FIG. 2).The width of the window 5 in the circumferential direction of thepolygonal cavity 3 is only significantly greater than the ball 6 whichforms the pressure-piece. In the insertion direction E, the window 5 hasan extent which is considerably greater than, even more than double thesize of, the diameter of the ball. Acting in this direction is acompression spring 8 which, on the one hand, is supported on a narrowwall of the window and, on the other hand, acts on the ball 6. Itsdirection of action is counter to the insertion direction E, so that adisplacement of the ball 6 in the insertion direction E results in thecompression spring 8 being compressed.

Without a bit inserted, the ball butts against the narrow wall 5′ of thewindow 5 on the opening side. In the direction of the center of thepolygonal cavity 3, the ball 6 is retained by carrying shoulders thatextend along the longitudinal walls of the window 5 and are spaced apartfrom one another by a clear distance which is slightly smaller than thediameter of the ball. In the opposite direction, the ball is retained byan actuating sleeve 7. The actuating sleeve 7 has a sloping inner wall9. This sloping inner wall 9 may be of rotationally symmetricalconfiguration, so that the actuating sleeve 7 can be rotated on thesections of the chuck 1 which form the polygonal cavity 3. The diameterof the ball 6 is greater than the thickness of the wall of the polygonalcavity. A wedge-shaped gap is formed between the slope 9 and theimaginary line of the edge of the polygon which is interrupted by thewindow, and this gap is tapered counter to the insertion direction E. Inthe tapered region, the extent of the gap-like clearance is smaller thanthe diameter of the ball 6, so that the ball, subjected to the action ofthe slope 9, can penetrate, according to region, into the polygonalcavity 3. In the broad region of the gap, the latter has a width whichis greater than, or at least equal to, the diameter of the ball, so thatthe ball 6 can pass out of the polygonal cavity 3 altogether by virtueof a corresponding displacement of the actuating sleeve 7.

The emerging of the ball out of the polygonal cavity occurs in two ways.On the one hand, by displacement of the ball in the insertion direction,the ball 6 sliding or rolling along the slopes 9. This is associatedwith a compression of the compression spring 8. On the other hand, theemerging of the ball 6 out of the polygonal cavity 3 results from adisplacement of the actuating sleeve 7 counter to the insertiondirection E. In this case, the slope 9 is displaced in the direction ofthe mouth opening of the polygonal cavity 3 in conjunction with acompression of the restoring spring 10, which retains the actuatingsleeve 7 in the clamping position.

The chuck functions as follows:

Without a bit inserted, the ball 6 is located in the positionillustrated in FIG. 3. If a bit is then inserted into the polygonalcavity 3, the slope 13 at the end of the polygonal section 2 displacesthe ball 6 in the insertion direction. The ball 6 then slides along thesloping inner wall 9 of the actuating sleeve 7, which is retainedstationary, the compression spring 8 being subjected to stressing in theprocess. It slides along the slope 9 until it has passed out of thepolygonal cavity 3 to a sufficient extent in order to slide the edge ofthe polygon of the polygonal section 2. This state is illustrated inFIG. 5. It can be seen there that the ball 6 is spaced apart from thenarrow wall 5′ of the window 5. The compression spring 8 retains theball 6 in a clamping position between the edge of the polygon of thepolygonal section 2 and the sloping inner wall 9. If the bit is thensubjected to a tensile force, the clamping action increases.

If the bit is to be removed from the chuck, then the actuating sleeve 7should be displaced into its release position counter to the insertiondirection E. This is illustrated in FIG. 4. The ball 6 is then displacedmomentarily into its position in which it acts on the narrow wall 5′ ofthe window 5. It can then move aside in a direction transverse to theinsertion direction E. It has a sufficient amount of play so that thebit can be drawn out of the polygonal cavity 3.

FIG. 6 shows a variant in which a polygonal section 2 of a bit with acorner cutout 11 has been inserted into the polygonal cavity 3. The ball6 can then—also with abutment against the wall 5′ of the window5—penetrate into the corner cutout 11 and thus, subjected to the actionof the sloping inner wall 9 on one side and penetrating, as it were, ina positively locking manner into the corner cutout 11, develop a meansfor preventing the bit from being drawn out. Here too, the bit isinserted without there being a requirement for the actuating sleeve 7 tobe actuated since, here too, the ball 6 can be displaced in the mannersillustrated in FIG. 7 by the slope 13 at the end of the polygonalsection 2.

It is also the case in this variant that the ball is freed by actuation,that is to say by displacement of the actuating sleeve 7, counter to theinsertion direction E. It can then emerge out of the corner cutout 11 ina direction transverse to the insertion direction E.

The configuration according to the invention is accompanied by theadvantage that the chuck can securely retain both polygonal sectionswhich have a corner cutout and those which do not have a corner cutout,this being done using one and the same ball.

All features disclosed are (for themselves) pertinent to the invention.The disclosure content of the associated/attached priority documents(copy of the prior application) are hereby also included in full in thedisclosure of the application, also for the purpose of incorporatingfeatures of these documents in claims of the present application.

1. Chuck (1) for tools, especially screwdriver bits with a polygonalsection (2), the chuck comprising: a polygonal cavity (3) for theinsertion of the polygonal section (2), a wall (4) of the polygonalcavity (3) having a window (5) in which is disposed a pressure-piece (6)which is displaceable in an insertion direction (E); wherein, in orderto secure the inserted polygonal section (2) against being drawn out,the pressure-piece (6) is forced against the polygonal section (2), in adirection transverse to the insertion direction (E), by a sloping innerwall (9) of an actuating element; wherein the actuating element isoutside the window and is retained in a clamping position by a restoringspring (10) acting in the insertion direction (E), and which, in arelease position of the actuating element (7), can move aside out of thepolygonal cavity (3) in order for the polygonal section (2) to be drawnout; and wherein the pressure-piece (6) is subjected to the action of acompression spring (8) acting counter to the insertion direction (E)and, upon a displacement counter to the direction of spring action ofthe compression spring, the pressure-piece (6) can move aside out of thepolygonal cavity (3).
 2. Chuck according to claim 1, wherein thepressure-piece (6) is a round piece.
 3. Chuck according to claim 1,wherein the pressure-piece (6) is a ball.
 4. Chuck according to claim 1,wherein the pressure-piece (6) is subjected to the action of a slopinginner wall (9) of an actuating sleeve which forms the actuating element(7).
 5. Chuck according to claim 1, wherein the window (5) is associatedwith one of the edges of the polygon of the cavity (3).
 6. Chuckaccording to claim 1, wherein the actuating element (7) is displaceablefrom the clamping position into the release position counter to theforce of the restoring spring (10).
 7. Chuck (1) for tools, especiallyscrewdriver bits with a polygonal section (2), the chuck comprising: apolygonal cavity (3) for the insertion of the polygonal section (2), awall (4) of the polygonal cavity (3) having a window (5) in which isdisposed a pressure-piece (6) which is displaceable in an insertiondirection (E); wherein, in order to secure the inserted polygonalsection (2) against being drawn out, the pressure-piece (6) is forcedagainst the polygonal section (2), in a direction transverse to theinsertion direction (E), by a sloping inner wall (9) of an actuatingelement; wherein the actuating element is outside the window and isretained in a clamping position by a restoring spring (10), and which,in a release position of the actuating element (7), can move aside outof the polygonal cavity (3) in order for the polygonal section (2) to bedrawn out; wherein the pressure-piece (6) is subjected to the action ofa compression spring (8) acting counter to the insertion direction (E)and, upon a displacement counter to the direction of spring action ofthe compression spring, the pressure-piece (6) can move aside out of thepolygonal cavity (3); and wherein the restoring spring (10) and thecompression spring (8) act in the same direction.
 8. Chuck according toclaim 1, wherein the pressure-piece (6) can penetrate, through thewindow (5), into a corner cutout (11) of the polygonal section (2). 9.Chuck (1) for tools, especially screwdriver bits with a polygonalsection (2), the chuck comprising: a polygonal cavity (3) for theinsertion of the polygonal section (2), a wall (4) of the polygonalcavity (3) having a window (5) in which is disposed a pressure-piece (6)which is displaceable in an insertion direction (E); wherein, in orderto secure the inserted polygonal section (2) against being drawn out,the pressure-piece (6) is forced against the polygonal section (2), in adirection transverse to the insertion direction (E), by a sloping innerwall (9) of an actuating element; wherein the actuating element isoutside the window and is retained in a clamping position by a restoringspring (10), and which, in a release position of the actuating element(7), can move aside out of the polygonal cavity (3) in order for thepolygonal section (2) to be drawn out; wherein the pressure-piece (6) issubjected to the action of a compression spring (8) acting counter tothe insertion direction (E) and, upon a displacement counter to thedirection of spring action of the compression spring, the pressure-piece(6) can move aside out of the polygonal cavity (3) ; and wherein thewindow (5) is configured as a slot extending in the insertion direction(E).
 10. Chuck (1) for tools, especially screwdriver bits with apolygonal section (2), the chuck comprising: a polygonal cavity (3) forthe insertion of the polygonal section (2), a wall (4) of the polygonalcavity (3) having a window (5) in which is disposed a pressure-piece (6)which is displaceable in an insertion direction (E); wherein, in orderto secure the inserted polygonal section (2) against being drawn out,the pressure-piece (6) is forced against the polygonal section (2), in adirection transverse to the insertion direction (E), by a sloping innerwall (9) of an actuating element; wherein the actuating element isoutside the window and is retained in a clamping position by a restoringspring (10), and which, in a release position of the actuating element(7), can move aside out of the polygonal cavity (3) in order for thepolygonal section (2) to be drawn out; wherein the pressure-piece (6) issubjected to the action of a compression spring (8) acting counter tothe insertion direction (E) and, upon a displacement counter to thedirection of spring action of the compression spring, the pressure-piece(6) can move aside out of the polygonal cavity (3); and wherein thewindow (5) is located level with a corner cutout (11) provided in atleast one of the edges of the polygon of the polygonal section (2).